High pressure fluid intensifier and method

ABSTRACT

A pressure intensifying apparatus to deliver a very high pressure stream of water through a nozzle. There is a single working piston having two pressure surfaces of a relatively large area, the working piston being connected to two high pressure pistons each having a pressure surface of a relatively small area. A control valve delivers a high pressure working fluid alternately to opposite sides of the working piston to cause it to reciprocate so that the pressure pistons alternately deliver water at high pressure to the nozzle. In shifting between its two end positions, the control valve passes through an intermediate position at which a restricted flow passage is provided for the working fluid, this restricted flow passage having an effective cross sectional area relative to the effective area of the discharge nozzle such that the back pressure of the restricted passage of the control valve matches the back pressure exerted on the working fluid so that a substantially constant back pressure is imposed on the high pressure source of working fluid. Further, there is a valve shifting mechanism comprising two shifting valves, each of which is responsive not only to physical contact by the working piston, but also to pressurization of its related working chamber to cause rapid shifting of the control valve.

United States Patent [191 Olsen men PRESSURE FLUID INTENSIFIER AND METHOD I John H. Olsen, Vashon, Wash. Flow Research, Inc., Kent, Wash.

Jan. 12, 1973 Inventor: Assignee: Filed:

Appl. No;

US. Cl 417/53, 91/306, 91/313,

Int. Cl. F04b 35/00, F011 25/04 Field of Search 91/305, 306, 307, 313;

References Cited UNITED STATES PATENTS 3,465,686 '9/19'69 Nugier 417/403 2,942,584 6/1960 Rethmeier 91/464 3,540,348 11/1970 Penther ..91/306 Primary Examiner-Carlton R. Croyle Assistant Examiner-Richard Sher v Attorney, Agent, or Firm-Graybeal, Barnard, Uhlir & v

Hughes [57] ,ABSTRACT A pressure intensifying apparatus to deliver a very high pressure stream of water through a nozzle. There is a single working piston having two pressure surfaces of a relatively large area, the working piston being .connected to two high pressure pistons each having a stricted passage of the control valve matches the back pressure exerted on the working fluid so that a substantially constant back pressure is imposed on the high pressure source of working fluid. Further, there is a valve shifting mechanism comprising two shifting valves, each of which is-responsive not only to physical contact by the working piston, but also-to pressurization of its related working chamber to cause rapid shifting of the control valve. I

16 Claims,

'15 Drawing Figures PATENTEDNAY 2 1 lam sum 2 0F 4 w 3v 3 0m PATENTEDIAYZIIBM 3811.795.

SBEEI t Of 4 FIGO 8 I I F160 9 a b FLOW I l QI PRESSURE WORKING TRANSFER FLUID I PORTS I I i 1 "I r I I I I I I A B c o E A a c 0 E VALVE POSITION I VALVE POSITION H F11 l24u" 5601 I I28 l28a I24 60a MG; III

, HIGH PRESSURE FLUID: INTENSIFIER AND METHOD BACKGROUND or THE INVENTION rapid reversal of the working piston so that there is no' significant interruption of the flow of high pressure output fluid. Yet another problem in the prior art is that of alleviating pressure surges in the working fluid while the working piston is being reversed. Aside from these with manys'uch prior art devices is that of obtaining a operational problems, there are, especially when very 4 high pressures are used, safety considerations with respect to one of the hydraulic lines or other components breaking or rupturing.

' Typical of the prior art deviceswhich show pressure intensifying systemsand various valve switching mechanisms adaptable for-such systems are the following U.S. Pats; Atkinson, No. 153,296; West et al., No.

2,000,805;Rethmeier, No. 2,942,584; Murray, No. 3,045,611; Pennther, No. 3,540,349; and Bowen, No.

It is an object of the present invention to provide a high pressure fluid intensifier having desirable operating features, particularly with respect to the problems and considerations mentioned above.

SUMMARY oi THE INVENTION In the apparatus of the present invention, there is a working cylinder in which a working piston is mounted for'reciprocating motion, the piston dividing the cylinder into first and second working chambers. Two high pressure pistons are connected to the working piston. in a manner that reciprocation of the working piston causes a flow of high. pressure fluid to be procuced altemately from the two high pressure pistons. The high pressure flow is directed through a discharge nozzle to produce a high velocity stream of water. Tocause reciprocation of the working piston, there is a control valve having first and second positions to deliver pressurized working fluid to, respectively, the first and second working chambers. According to one facet of the present invention, the control valve has a third intermediate position through which it passes in moving between its first and second positions. In the intermediate position pressurized working fluid is directed through a pressure reducing flow passage, which produces a back pressure substantially balancing the back pressure resulting from transmitting power through the working piston and the pressure intensifying pistons to produce a high pressure fluid flow through the output nozzle. Thus, during reversal of the working piston when the control valve passes through its intermediate position, any substantial surge of back pressure against the working fluid source is alleviated.

- In accordance with another facet of the present invention, there are two shifting valves to cause the control valve to move between its first and second positions. Each shifting valve 'is made responsive not only tomovement of the piston to an end limit of travel proximate the-shifting valve, but is responsive also to pressurized working -fluid in its respective chamber being at a predetermined level. Actuation of one or the other of the shifting valves causes a pressure imbalance at the control valve to cause rapid shifting of the control valve. A centering spring urges the control valve toward its intermediate position. If there is a pressure reduction in the working chamber that is pressurized at any particular moment, for example by a rupture in one of the high pressure output lines, the decrease in pressure causes deactivation of its related shifting valve to move the control valve to its intennediate position and stop further operation of the apparatus.

Other more specific features of the present invention a will become apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a semi-schematic side elevational view of the overall apparatus ,of the present invention;

FIG. 2 is a viewpartly in sections of the pressure intensifying apparatus of the present invention;

FIG. 3 is a sectional view of one of the shifting valves of the apparatus of FIG. 2;.

FIGS. 46 are semi-schematic drawings illustrating the operating'sequence of the present invention;

FIGS. 7A-7E are a series of semi-schematic'drawings showing the sequence of operation of the control valve of the present invention; 1

FIG. 8 is a graph illustrating the flow characteristics in the control valve in the sequence of operation of FIGS. 7A-7E; I

FIG. 9 is a graph illustrating the pressure characteristics-of the control valve in the sequence of operation of FIGS. 7A-7 E; I

FIG. 10 is a semi-schematic illustration of a second embodiment of the control valve of the present inventron;

' FIG. ;11 is a semi-schematic drawing of a third embodiment of the control valveof the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, there is shown an electricmotor 10 which drives a hydraulic pump 14, which in turn supplies working fluid to a pressure intensifier unit 16. The intensifier l6 draws fluid (i.e., water) from a suitable source, such as-a reservoir 18, and discharges the water at av'ery high pressure throughan'output, which as shown herein is a tube 20 with a small area exit nozzle 22. This results in a discharge of a fluid jet stream of a small diameter (e.g., 0.03 inches) and a very high velocity (e.g., 1,200 feet per second or greater).

In describing the present invention in detail, first the physical components of the pressure intensifying unit 16 will be described with reference to FIGS. 2 and 3. Second, the overall operation of the total apparatus will be described with reference to the sequential schematic drawings of FIGS. 4 through 6. Thereafter, the precise manner in which the control valve 38 functions to actial illustrations of FIGS. 7A through 7E, and the two graphs of FIGS. 8 and 9, with two modified valves being shown in FIGS. 10 and 11.

The physical components of the pressure intensifying unit 16 are illustrated in FIG. 2. For clarity of illustration, the various fluid lines and passages built into or attached to the unit 16 are not illustrated in FIG. 2, but rather are shown schematically in FIGS. 4 through 6. With reference to FIG. 2, the pressure intensifying unit 16 comprises a main housing 24, comprising a main cylinder 26, right and left end bell members 28 and 30, respectively, mounted to the ends of the cylinder 26, and right and left high pressure cylinders 32 and 34, respectively, threaded into respective bells 28 and 30. Connected to the housing 24 is a manifold block 36 on which is mounted a flow'control valve 38.

Mounted for reciprocating motion within the housing 24 is a unitary piston assembly 40. This assembly comprises a larger diameter central working piston 42 mounted within the main cylinder 26, and right and left high pressure pistons 44 and 46, respectively, extending oppositely from the center working piston 42. The working piston 42 divides the interior of the main cylinder 26 into right and left working chambers 48 and 50 respectively. The high pressure piston 44 reciprocates in the right high pressure chamber 52 defined by the right cylinder 32, while the left high pressure piston 46 reciprocates in the left high pressure chamber 54 defined by the other cylinder 34.

The aforementioned control valve 38 comprises a valve housing'56 defining a transfer chamber 58, in which is slide mounted a valve spool 60. In the housing 56 is a centrally located high pressure fluid inlet port 62, right and left transfer ports 64 and 66, respectively, on opposite sides of the inlet port 62, and right and left low pressure outlet ports 68 and 70, respectively, positioned outside of the two transfer ports 64 and 66.

The valve spool 60 comprises right and left lands or pistons 72 and 74, respectively, and right and left outermost end closure members 76 and 78, respectively. Outside the two closure members 76 and 78 are respective right and left centering springs 80 and 82, respectively, which urge the spool 60 to its center position in the housing 56; each of the springs 80 and 82 has a stop collar 83 engaging a stop shoulder 83a to prevent either spring 80 or 82 urging the valve spool 60 beyond its center position.

The center port 62 is connected to a high pressure line from the pump 14, while the ports 68 and 70 are connected to the low pressure return line of the pump 14. The right transfer port 64 connects to the right working chamber 48, and the left transfer port 66 connects to the left working chamber 50. The groove or chamber 84a located between the two piston elements 72 and 74 is a high pressure fluid transfer chamber, and functions to direct high pressure fluid from the port 62 to either the right transfer port 64 or the left transfer port 66 when in, respectively, a right or left hand position. The right piston 72 and the right closure piston 76 define a groove or chamber 84b which is a low pressure transfer chamber that functions to connect the transfer port 64 with the low pressure outlet port 68 when the spool 60 is in its left hand position. In like manner, the left transfer piston 74 and left closure piston 78 define therebetween a groove or chamber 84c which functions to connect the left transfer port 66 with the low pressure outlet port when the spool 60 is in its right hand position.

To move the spool 60 of the valve 38 between its right and left positions, there are two shifting valves 85 and 86, respectively, located in, respectively, the right and left bell sections 28 and 30 of the housing 24. For convenience of illustration only the right shifting valve 85 is shown in section in FIG. 2 (the valve 85 and 86 being substantially identical). Each of the valves 85 and 86 comprises a sleeve 88 in which is slidably mounted a plug 90. There is an inlet port 92 and an outlet or venting port 94, the port 92 being closed from the venting port 94 when the valve is in the closed position shown in FIG. 2. The plug is urged to its closed position by a compression spring 96. To open the valve 85 or 86 there is provided an actuating pin 98 which butts against the plug 90 and extends through the housing to project into the end of its respective working chamber 48 or 50. A locating stop 100 on the pin 98 properly positions the plug 90 in its closing position with the pin 98 extending into the chamber 48 or 50. Through holes 101 in the plug 90 permit flow from the inlet port 92 to the venting port 94 when the plug 90 is pushed by pin 98 against the urging of the spring 96 to its open position shown in FIG. 3. The inlet port 92 of the right shifting valve 85 is connected through an end opening 102 in the housing 56 of the valve 38 to a right control chamber 104 at the right end of the spool 60 of the valve 38, while the inlet port 92 of the left shifting valve 86 is similarly connected to the left control chamber 105 through opening 103 in the left of the valve 38.

In describing the operations of this apparatus, for convenience the overall operation will first be described and then the means for starting the pumping action. In FIG. 4, the valve 38 is in its left hand position,

so that high pressure fluid from the high pressure line 106a of the pump 14 is directed into the left working chamber 50, while the right working chamber 48 is connected through a low pressure return line l06b to the fluid reservoir 107 of the pump 14. This causes the working piston 42 to move to the right, as seen in FIG. 4, which in turn causes the right high pressure piston 44 to force output fluid from the high pressure chamber 52 through a check valve 108 and out the discharge nozzle 22. At the same time, output fluid is being drawn from the source 18 through a check valve 109 into the left high pressure chamber 54.

The pumping pressure of the pump 14 is sufficiently large, relative to the force of the return springs 96 and the cross sectional area of the actuating pins 98 of the shifting valves 85 and 86, that when one of the working chambers 48 or 50 is pressurized by the pump 14, the resulting pressure on its related actuating pin 98 is suff cient to force the pin 98 against the urging of its related spring 96 to open the valve 85 or 86. A portion of the high pressure working fluid is directed from the pump 14 to the valve control chambers 104 and 105 through respective restricted flow orifices 110 and 112, and also to the high pressure inlet ports 92 of the shifting valves 85 and 86. The venting port 94 of each shifting valve 85 or 86 is connected to the pump reservoir 107. Thus, when one of the valves 85 or 86 is closed, its related valve control chamber .104 or 105, respectively, is pressurized, but when one of the valves 85 or 86 is open, its respective valve control chamber 104 or 105 is depressurized. 1

With reference to FIG.4, since the working chamber 50 is pressurized from the pump 14, the shifting valve pin 98 protrudes into the chamber 48, so that the shifting valve 85 is closed, with theright valve control chamber 104 being pressurized. The differencein pressure in the two valve control chambers E04 and E05 holds the spool element 60 of the valve 38 in its left hand position against the urging of the spring 82 as seen in FIG. 4.

As the working piston 42 continues to move to the right, it approaches its end limit of travel as shown in FIG. 5. Near its end limit of travel, the piston 42 engages the actuating pin 98 to push the pin 98 and the plug 90 of the shifting valve 85 to its open position to depressurize the rightvalve control chamber 104. With both the control chambers I04 and 105 depressurized, the left centering spring 82 pushes the spool element 60 toward its center position, as shown in FIG. 5.

When the spool element 60 reaches its center position, two things occur. F irst,- both of the working champressure supply line 1106a from the pump 14 becomes I working chambers 48 and 50 is to permit the spring 96 to move the left shifting valve 86 outwardly toward the left working chamber 50 to close the left shifting valve 86 and thus cause immediate pressurization of the left valve control chamber 105. This immediately causes the spool element 60 to continue movement through its center or intermediate position to its right position, shown in FIG. 6, where high pressure working fluid is delivered to the working chamber 48, with the left working chamber 50 being connected to the low pressure line 106 leading to the pump reservoir 107.

With the right working chamber 48 now pressurized, the working piston 42 moves to the left so that the left high pressure piston 46 forces output fluid from the left high pressure chamber '54 through a check valve 116 and out the output nozzle 22, At the same time, additional output fluid is being drawn into the right high pressure chamber 52 through a check valve 148. With the right working chamber 48 pressurized, as the working piston 42 moves away from physical engagement with the right actuating pin 98, the pressure of the working fluid in the chamber 48 keeps the right actuating pin 98 in its retracted position to maintain the right shifting valve 85 in its open position and maintain the depressurization of the right valve control chamber 404 so that the spool element 60 remains in'its right position, as shown in FIG. 6 because of the pressurization of the left valve control chamber I05 due to the left shifting valve 86 being closed.

When the working piston 42 moves toward its left end position to engage the left actuating pin 98, a simience to FIG. 5, to reverse the fluid flow in the working chambers 48 and 50 and cause the working piston42 to begin movement back to the right.

To initiate operation of the apparatus, there is provided a starting valve, this being shown schematically at 120. The valve 120 has an up position where the right valve control chamber 104 is directly connected to the reservoir 107, a down position where the left valve control chamber 105 is connected to the reservoir 107, and an intermediate position where the valve 120 provides no operative connection to the chambers 104 and 105. In the three illustrations of FIGS. 4 through 6, the starting valve 120 is shown in its center position where it has no effecton the operation of the apparatus. To describe the operation of the starting valve 120, let it be assumed that the pump 14 has been turned off and theentire system has become depressurized, with the spool element of the valve 38 returning to its center position by action of the center-ing springs and 82. Further, let it be assumed that the working piston 42 is in some intermediate position, as shown in FIG; 4.

When the pump 14 is started, with the valve spool element 60 in its center position, neither of the working chambers 48 or 50 becomes pressurized. However, both of the valve control chambers 104 and are pressurized, since both of the shifting valves 85 and 86 remain'closed. These circumstances contribute. to the safety of the operation in that the intensifying unit 16 will not inadvertently start pumping when the hydraulic pump is started, provided that piston 42 is not at that moment holding either valve 85 or 86 open. It should be noted that when the motor is turned off to stop the pumping action, there is a gradual decline of hydraulic pressure due to the inertia of the motor and pump. If the motor is turned off and the hydraulic 'pres-' that pin 98 allowing the valve 85 or 86 to close and cause the control valve 38 to return to its center position where neither of the working chambers 48 and 50 is pressurized. Thus, piston 42 will stop in a position relar shifting sequence occurs, as described with refermote from pins 98, and when the motor 10 is restarted,

the pumping action will not startjBy pushing the valve to its down position, the left control chamber 105 becomes exposed to the low pressure pump reservoir 107 so that the high pressure in the right valve control chamber 104 causes the valve element 60 to move to the left (i.e., the position shown in FIG. 4.) to cause the piston 42 to move to the right. As soon as the working piston 42 reaches its full right position to. engage the right actuating pin 98, the normal shifting sequence goes into effect as described above herein. By moving the starting valve 120 to its up position to cause the draulic lines so that the'normal shifting sequence becomes operative, with the working piston 42 then reciprocating with automatic shifting of the valve 38 as described above.

In the event that there is a break in one of the high pressure output lines to the nozzle 22, there will be an immediate drop in pressure in the output chamber 52 or 54 that is at the time pressurized, and a corresponding drop in pressure in the related working chamber 48 or 50, which happens to be pressurized at that particular instant. When there is such a pressure drop in the pressurized working chamber 48 or 50, its related actuating pin 98 is moved outwardly by spring 96 to its valve closing position to close its related shifting valve 85 or 86 to pressurize its related valve control chamber 104 and 105 (both chamber 104 and 105 then being pressurized) so that the valve element 60 returns to its center position by action of the centering springs 80 and 82 to vent both working chambers 48 and 50 to low pressure and halt movement of the working piston 42. Thus, in the event of any break in the high pressure lines, the system immediately shuts itself off.

To describe in more detail the operation of the control valve 38, reference is now'made to FIGS. 7A through 7E.

In FIG. 7A, the spool element 60 is shown in its full left position (shown schematically in FIG. 4), where the right piston 72 is positioned between the'high pressure port 62 and the right transfer port 64 so as to block any flow therebetween, while the left piston 74 is positioned so as to block any flow from the left transfer port 66 into the low pressure outlet port 70. In this position, there is free flow from the high pressure port 62 to the left transfer port 66 through the center high pressure chamber 84a to pressurize the working chamber 50 as described above. Also, the right transfer port 64 communicates with the low pressure port 68 through the right low transfer chamber 84b sovthat the right working chamber 48 is depressurized. As described above, thespool element 60 remains in this position until working piston 42 reaches its extreme right end of travel to cause shifting of the valve spool element 60 to the right.

In FIG. 7B, the valve element 60 is shown moving from its extreme left hand position through a position where it is just about to enter its intermediate position. It will be noted that the laterally outermost portion 122 of the circumferential surfaces of each of the pistons 72 and 74 is substantially cylindrical so that it fits against the inner cylindrical surface of the housing 56. However, the laterally inward circumferential surface portion 124 of each of the pistons 72 and 74 (i.e., those surface portions closer to the center of the spool element 60) are tapered very moderately inwardly toward the middle of the spool element 60. For purposes of illustration, this taper is shown to be at a somewhat larger angle than normally used, this taper ordinarily being in the order of one degree from the longitudinal axis of the spool element 60. It can be seen that in the position shown in FIG. 7B the tapered surface 124 of the left piston 74 forms with the inner edge 126 of the left transfer port 66 a restricted circumferential flow passage 128.

As the piston continues to move from the position FIG. 78 toward the position of FIG. 7C, where the spool element 60 is centered, a passage opens at 130 from the left transfer port 66 through the left low pressure transfer chamber 84c to the low pressure outlet port 70. Because of the very shallow taper of the surface 124, as soon as the spool element 60 moves a very short distance from the position of FIG. 7B, the passageway has a much larger cross sectional area than the passage of 128, so that there is a large pressure drop from the inlet port 62 across the passageway 128, and the pressure in the transfer port 66 almost immediately drops to the pump reservoir pressure that exists in the outlet port 70. As the spool 60 continues to move to the right from position 78 to that of 7C the left flow passage 128 becomes more restricted, while the right flow passage 128 defined by the piston 72 with the housing 56 becoming less restricted. Since the tapered surfaces 124 are both uniform, the rate of decrease of the cross section of the left restricted passage 128 is substantially the same as the rate of increase of the cross sectional area of the right restricted flow passage 128, so that the total flow rate through both passages 128 is constant. This is illustrated in the graph of FIG. 8, where the flow through the left restricted flow passage 128 is indicated at a and the right restricted flow passage 128 is indicated at b, with the combined-flow through both passages 128 being shown by the dotted line at c.

In the graph of FIG. 9, the pressure in the left transfer port 66 is indicated at a, while the pressure in the right transfer port 64 -is indicated at b, in the travel of the spool element 60 from the position of FIG. 7A to that of FIG. 7B.

When the spool element 60 is traveling through its intermediate position (i.e., from the position of FIG. 7B, through the position of FIG. 7C to the position of FIG. 7D), both the right and left transfer ports 64 and 66 are at the low pump reservoir pressure since the flow passages 130 have a substantially larger cross sectional flow area than the passages 128 (in the order of perhaps one hundred times as great when the spool element 60 is in the, position of FIG. 7C).

As described previously herein, as soon as the pressurized working chamber 48 or 50 becomes depressurized, there is an immediate pressure imbalance in the two valve control chambers 104 and 105, which causes the spool element 60 to continue movement through its center postion to its other end position. When the spool element reaches the position shown in FIG. 7D, the spool element 60 is now moving from its intermediate position to its right position. At this point, the left restricted flow passage 128 is being completely closed off, while theright restricted flow passage 128 has reached its maximum effective cross'sectional flow transfer port 64 to cause pressurization of the right working chamber 48.

It is important to note that the total cross sectional area of the two restricted flow passages 128 remains substantially constant as the spool element 60 is moving through its intermediate phase from the position of FIG. 7B to that of 7D. These two restricted flow passages 128 are, in effect, the same restricted flow pastially the same as the pressure existing-in either of the working chambers 48 and 50 when pressurized with the control Valve 38 in either'it's right or left position. The effect of this is that when the valve element 60 is mov- 'ing from its right position through its intermediate position to its left position or vice versa, the back pressure exerted on the high pressure line from the pump 14 remains substantially constant, with the only pressure surges experienced being those caused by inertial forces of reversing the working piston 42.

The pressure balance is accomplished by properly selecting the effective total cross sectional area of the passages 128 relative to the effective cross sectional flow area of the output nozzle 22 and also relative to the effective pressure areas of the working piston 42 and the high pressure pistons 44 and 46, and to the frictional forces acting on the piston-assembly. To explain this relationship let us first assume these frictional forces are negligable and represent only a small correction to the relationship. It should be pointed out that the ratio of the pressure in either of the high pressure chambers 52 or 54 to the pressure in the working chamber 50 is'inversely proportional to the area of the piston 44 (which is the square of the radius of the piston 44 times 7r). and proportional to the working area i of the low pressure piston 42 (which is the square of the radius of the piston 42 times 11 minus the cross sectional area of the piston 44). The pressure drop through the output nozzle 22 is proportional to the square of the average velocity of fluid flowfrom the nozzle 22 times the density of the output fluid (i.e., water). Likewise, the pressure drop across the flow passages "128 is proportional to the square of the average flow velocity of the fluid through the passages 128 times the density of the working fluid from the pump 14. Thus, the effective cross sectional flow area of the passages 128, or of the passage shown schematically at 114, should be proportional to the effective cross sectional flow area of the nozzle 22 times the working area of the low pressure piston 42, divided by the pressure area of either of the pressure pistons 44or 46, multiplied by the square root of the ratio of the pressure area of the working piston 42 to the pressure area of the high pressure piston 44 and 46, multiplied by thev square root of the ratio of the density of the working fluid to the density of the output fluid. Expressed mathematically, this relationship can be stated as follows:

u v n An w/Ap)( ii w n UDw/D o D the density of the working fluid D the density of the output fluid To givea numerical example, let it be assumed that the densities of theworking fluid and output fluid are approximately equal, that the discharge coefficients are equal, and that the effective working area of the piston 42 is approximately four times the working area of either of the pressure pistons 44 or 46. The total flow of working fluid into either of thelow pressure chambers 48 or 50' would be four times the flow from either of the high pressure chambers 52 and 54. According to the above formula, thetotal effective cross sectional flow area of the restricted valve passageway (either the passages 128 or the schematic passage 114), should be eight times the effective cross sectional flow area of the nozzle 22. In practice the passages 128 would be chosen slightly smaller to correct for the additional pressure required for overcoming friction.

In FIG.' 10, there is shown a second embodiment of the control valve of the present invention, in which components corresponding to thevalve 38 of the first embodiment will be given like numerical designations, with an a suffix distinguishing those of the second embodiment. Thus there is a housing 56a in which is mounted a valve spool 60a, comprising right and left pistons'72a and 74a, respectively, and right and left outermost end closure members 76a and 78a. However, instead of forming the inner circumferential surface portions of the pistons 72a and 74a with a tapered surface, these surface portions of the piston element 72a and 74a are stepped radially inwardly as at 124a. Thus, when the valve element 60a passes through its intermediate position (corresponding to the movement of the valve element of the first embodiment as it moves from the position of FIGS. 7B to the position of FIG. 7D), there are two restricted flow passages 128a, through which there are substantially equal flows. As in the first embodiment, the combined effective cross sectional flow area of the two passages of 128a is such as toapproximate the back pressure exerted from the output nozzle back through the system to the pressurized working fluid.

A third embodiment of the control valve of the present invention is illustrated in FIG. 11, In this valve, there is a housing in which there is a movable valve element 142 comprising a center piston 144 and two side pistons 146 and 147, respectively, and two end closure pistons 148 and 149, respectively. There is a center high pressure inlet port 150, right and left transfer ports 152 and 154, respectively, on opposite sides of the port 150, and right and left low pressure ports 156 and 158, respectively, located outside .the ports 152 and 154.

These components are arranged so that when the valve element 142 is in the right hand position, the right transfer port 152 communicates with the. low pressure port 156 to permit outflow of working fluid from its related working chamber, while high pressure fluid is being directed from the port through thetransfer port 154 to pressurize the other working chamber.

which perform substantially the same function as the aforementioned flow passages 128 and 128a of the first and second embodiments. For this reason, no detailed description will be provided of the operation of this valve of the third embodiment, since it is apparent from the description of the operation of the prior two embodiments of the control valve.

What is claimed is:

l. A hydraulic power apparatus for operation, for example, as a pressure intensifying system to deliver a high pressure flow of output fluid, said apparatus comprising: I

a. a working cylinder,

b. a working piston mounted in said working cylinder and separating said working cylinder into first and second working chambers, said working piston and cylinder being so arranged with inlet and outlet passage means as to receive pressurized working fluid of at least a predetermined pressure level alternately into said first and second working chambers, to cause said piston to reciprocate between opposite first and second end positions in said cylinder,

. a control valve means to direct pressurized fluid from a working fluid source alternately to said first and second working chambers to cause the reciprocation of said working piston, said control valve means having first and second positions to direct pressurized fluid alternately to respectively said first and second working chambers,

d. a first shifting valve means operatively connected to said control valve means and having an actuating position where it causes said control valve means to be positioned in its first position to deliver pressurized working fluid to said first working chamber, said first shifting valve having first actuating means to move said first shifting valve means to its actuating position, which first actuating means is responsive to the piston moving to one of its end positions of travel and also responsive to working fluid mom of said chambers being at said predetermined pressure level, and

e. a second shifting valve means operatively connected to saidcontrol valve means and having an actuating position where it causes said control valve means to be positioned in its second position to deliver pressurized working fluid to said second working chamber, said second shifting valve means having second actuating means to move said second shifting valve means to its actuating position, which second actuating means is responsive to said piston'moving to the other of its end positions of travel and also responsive to working fluid in the other of said chambers being at said predetermined level.

2. The apparatus as recited in claim 1, wherein the actuating member of each shifting valve means is positioned to be moved to its acutating position by engagement of said piston at its respective end position of travel, and also moved to its actuating position by exposure to pressure at said predtermined level in its respective working chamber.

3. The apparatus as recited in claim 2, wherein said actuating member extends into an end of its respective working chamber and is urged by yielding means to extend into its respective working chamber.

4. The apparatus as recited in claim 1, wherein said control valve means has first and second control chambers, which, when pressurized and depressurized, move said control valve means between its first and second positions, said first shifting valve means being operatively connected to the first control chamber so as to reduce pressure in said first control chamber to move the control valve means to its first position, and said second shifting valve means being operatively connected to the second control chamber so as to reduce pressure in said second control chamber to move the control valve means to its second position.

5. The apparatus as recited in claim 4, wherein there are other positioning means for said valve control means, which other positioning means urges said control valve means to an intermediate position between said first and second positions, where working fluid at said predetermined pressure level is delivered to neither of the working chambers.

6. The apparatus as recited in claim 5, wherein said other positioning means comprises spring means which resiliently urges said control valve means to its intermediate position.

7. The apparatus as recited in claim 5, wherein said control valve means at its intermediate position functions to connect both said first and second working chambers to a low pressure area.

8. The apparatus asrecited in claim 4, further comprising other valve operating means having a first position wherein said first control chamber is exposed to low pressure, and a second position wherein said second control chamber is exposed to low pressure, whereby said control valve means can be moved between its first and second positions by operation of said other valve operating means.

9. A hydraulic power apparatus for operation, for example, as a pressure intensifying system, to deliver a high pressure stream of output fluid, said apparatus comprising:

a. a working cylinder,

b. a working piston mounted in said working cylinder and separating said working cylinder into first and second working chambers, said working piston and cylinder being so arranged as to receive pressurized working fluid of at least a predetermined pressure level alternately into said first and second working chambers, to cause said piston to reciprocate between opposite first and second end positions in said cylinder,

c. a control valve means to direct pressurized working fluid from a working fluid source alternately to said first and second working chambers to cause the reciprocation of said working piston,

1. said control valve means having-a first position where it delivers pressurized working fluid to said first chamber, a second position where it delivers pressurized working fluid to said second chamber, and a third intermediate position where said first and second working chambers are connected'to a lower pressure area,

2. said control valve means having first and second control chambers, which, when pressurized and depressurized, moves said control valve means between its first and second positions,

3. said control valve means having other valve positioning means arranged to urge said control valve means to its intermediate position,

l3 d. a first and second valve shifting means operatively connected to the control chambers of the control valve means in a manner to cause movement of the control valve means between its first and second positions, the first valve shifting means having an actuating position in which it is located-by said piston moving to one of its end positions of traveland also by action of said pressurized working fluidat said predetermined level in one of said chambers against said shifting valve means, said second shifting valve means also having an actuating position at which it is located by action of the piston moving to the other of its end positions of travel and also by pressurized working fluid at said predetermined level in the other of said working chambers acting against said second shifting valve means.

10. The apparatus as recited in claim 9, wherein said first shifting valve means is operatively connected to the first control chamber so that with said first shifting valve means in its actuating position pressure is reduced in said first control chamber so as to cause movement of the control valve means to its first position, and said second shifting valve means being operatively connected tosaid second control chamber so that with said second shifting valve means in its actuating position'pressure is reduced in said second control chamber to move said control valve means to its second position. 1

11. The apparatus as recited in claim 10, wherein each of said'shifting valve means comprises an actuating memberwhich is positioned to be moved to its actuating position'by engagement with said piston at its related end position of travel-and. also positioned to. be exposed to pressure in its related working chamber to be moved to its actuating position.

12. The apparatus as recited in claim 11, wherein said other positioning means comprises spring means which resilientlyurges said control valve means to its intermediate position.

13. The apparatus as recited in claim 9, further comprising other valve operating means having a first position wherein said first control chamber is exposed to low pressure, and a second position wherein said sec- .ond control chamber is exposed to low pressure,

whereby said control valve means. can be moved between its first and second positions by operation of said other shifting valve means.

1.4... A hydragljgpgwer apparatus for operation as a pressure intensifying system to' delivr a high isatr flow of output fluid said apparatus comprising:

a.' a working cylinder,

b. a working piston mounted in said working cylinder and separating said working cylinder into first and second working chambers, said working piston and cylinder being so arranged with inlet and outlet passage means as to receive pressurized working fluid of at least a predetermined pressure level alternately into said first and second workingchambers, to cause said piston to reciprocate between opposite first and second end positions in said cylinder, r

c. first and second high pressure output piston means operatively connected to said working piston so as to be moved along reciprocating paths thereby to deliver a high pressure flow of output fluid,

d. a control valve means to direct pressurized working fluid from a working 'fluid source alternately 'to said first and second working chambers to cause the reciprocation of said working piston, I 1. said control valve means having a first position where it delivers pressurized working fluid to said second chamber to cause said working piston to move to its first end position, a second position where it delivers pressurized fluid to said first working chamber to cause said working piston to move to its second end position, and a third intermediate position where said first and second working chambers are connected to a lower pressure area,

2. said control valve having first and second control chambers, which, when pressurized and depressurized, moves said control valve means between its first and second positions,

3. said control valve means having other valve positioning means arranged to urge said control valve means to its intermediate position,

sition and operatively connected to said first control chamber so as to depressurize said first control chamber when in its actuating position so as to ini-' tiatemovement of said control valve means from its first .position toward its second position, said first valve shifting means being responsive to move to its actuating position both by said working piston moving to its first position and by pressure in said first-working chamber being at saidpredetermined 1 pressure level, n v f. a second valve shifting means having an actuating position and operatively connected to said second control chamber so as to depressurize said second control chamber when in its actuating position so as to initiate movement of said control valve means from its second position toward its first position,

said second valve shiftirigmeans being responsive its non-actuating position, and causes continued movement of said control valve means to its opposite position, thereby effecting rapid response of said control valve means betweenits first and second positions.

15. The apparatus as recited in claim lfl wh erein saiclbtlier valve positioning nieaiisTor said control valve means comprises spring means to urge said control valve means to its intermediate position.

1 The apparatus as recited in claim 14, wherein each or said shifting valve meaiis comprisafiactuating member extending into a related working chamber, whereby each of said actuating members is responsive to pressure in its related chamber as well as to engagement of said working piston.

. a first valve shifting means having an actuating po- 

1. A hydraulic power apparatus for operation, for example, as a pressure intensifying system to deliver a high pressure flow of output fluid, said apparatus comprising: a. a working cylinder, b. a working piston mounted in said working cylinder and separating said working cylinder into first and second working chambers, said working piston and cylinder being so arranged with inlet and outlet passage means as to receive pressurized working fluid of at least a predetermined pressure level alternately into said first and second working chambers, to cause said piston to reciprocate between opposite first and second end positions in said cylinder, c. a control valve means to direct pressurized fluid from a working fluid source alternately to said first and second working chambers to cause the reciprocation of said working piston, said control valve means having first and second positions to direct pressurized fluid alternately to respectively said first and second working chambers, d. a first shifting valve means operatively connected to said control valve means and having an actuating position where it causes said control valve means to be positioned in its first position to deliver pressurized working fluid to said first working chamber, said first shifting valve having first actuating means to move said first shifting valve means to its actuating position, which first actuating means is responsive to the piston moving to one of its end positions of travel and also responsive to working fluid in one of said chambers being at said predetermined pressure level, and e. a second shifting valve means operatively connected to said control valve means and having an actuating position where it causes said control valve means to be positioned in its second position to deliver pressurized working fluid to said second working chamber, said second shifting valve means having second actuating means to move said second shifting valve means to its actuating position, which second actuating means is responsive to said piston moving to the other of its end positions of travel and also responsive to working fluid in the other of said chambers being at said predetermined level.
 2. The apparatus as recited in claim 1, wherein the actuating member of each shifting valve means is positioned to be moved to its acutating position by engagement of said piston at its respective end position of travel, and also moved to its actuating position by exposure to pressure at said predtermined level in its respective working chamber.
 2. said control valve means having first and second control chambers, which, when pressurized and depressurized, moves said control valve means between its first and second positions,
 2. said control valve having first and second control chambers, which, when pressurized and depressurized, moves said control valve means between its first and second positions,
 3. The apparatus as recited in claim 2, wherein said actuating member extends into an end of its respective working chamber and is urged by yielding means to extend into its respective working chamber.
 3. said control valve means having other valve positioning means arranged to urge said control valve means to its intermediate position, e. a first valve shifting means having an actuating position and operatively connected to said first control chamber so as to depressurize said first control chamber when in its actuating position so as to initiate movement of said control valve means from its first position toward its second position, said first valve shifting means being responsive to move to its actuating position both by said working piston moving to its first position and by pressure in said first working chamber being at said predetermined pressure level, f. a second valve shifting means having an actuating position anD operatively connected to said second control chamber so as to depressurize said second control chamber when in its actuating position so as to initiate movement of said control valve means from its second position toward its first position, said second valve shifting means being responsive to move to its actuating position both by said working piston moving to its second position and by pressure in said second working chamber being at said predetermined pressure level, whereby when said working piston reaches one of its end positions of travel, the working piston moves a proximate shifting valve to its actuating position to cause movement of said control valve means through its intermediate position, thereby causing a pressure reduction in the previously pressurized working chamber so that the other of said shifting valve means moves to its non-actuating position and causes continued movement of said control valve means to its opposite position, thereby effecting rapid response of said control valve means between its first and second positions.
 3. said control valve means having other valve positioning means arranged to urge said control valve means to its intermediate position, d. a first and second valve shifting means operatively connected to the control chambers of the control valve means in a manner to cause movement of the control valve means between its first and second positions, the first valve shifting means having an actuating position in which it is located by said piston moving to one of its end positions of travel and also by action of said pressurized working fluid at said predetermined level in one of said chambers against said shifting valve means, said second shifting valve means also having an actuating position at which it is located by action of the piston moving to the other of its end positions of travel and also by pressurized working fluid at said predetermined level in the other of said working chambers acting against said second shifting valve means.
 4. The apparatus as recited in claim 1, wherein said control valve means has firsT and second control chambers, which, when pressurized and depressurized, move said control valve means between its first and second positions, said first shifting valve means being operatively connected to the first control chamber so as to reduce pressure in said first control chamber to move the control valve means to its first position, and said second shifting valve means being operatively connected to the second control chamber so as to reduce pressure in said second control chamber to move the control valve means to its second position.
 5. The apparatus as recited in claim 4, wherein there are other positioning means for said valve control means, which other positioning means urges said control valve means to an intermediate position between said first and second positions, where working fluid at said predetermined pressure level is delivered to neither of the working chambers.
 6. The apparatus as recited in claim 5, wherein said other positioning means comprises spring means which resiliently urges said control valve means to its intermediate position.
 7. The apparatus as recited in claim 5, wherein said control valve means at its intermediate position functions to connect both said first and second working chambers to a low pressure area.
 8. The apparatus as recited in claim 4, further comprising other valve operating means having a first position wherein said first control chamber is exposed to low pressure, and a second position wherein said second control chamber is exposed to low pressure, whereby said control valve means can be moved between its first and second positions by operation of said other valve operating means.
 9. A hydraulic power apparatus for operation, for example, as a pressure intensifying system, to deliver a high pressure stream of output fluid, said apparatus comprising: a. a working cylinder, b. a working piston mounted in said working cylinder and separating said working cylinder into first and second working chambers, said working piston and cylinder being so arranged as to receive pressurized working fluid of at least a predetermined pressure level alternately into said first and second working chambers, to cause said piston to reciprocate between opposite first and second end positions in said cylinder, c. a control valve means to direct pressurized working fluid from a working fluid source alternately to said first and second working chambers to cause the reciprocation of said working piston,
 10. The apparatus as recited in claim 9, wheRein said first shifting valve means is operatively connected to the first control chamber so that with said first shifting valve means in its actuating position pressure is reduced in said first control chamber so as to cause movement of the control valve means to its first position, and said second shifting valve means being operatively connected to said second control chamber so that with said second shifting valve means in its actuating position pressure is reduced in said second control chamber to move said control valve means to its second position.
 11. The apparatus as recited in claim 10, wherein each of said shifting valve means comprises an actuating member which is positioned to be moved to its actuating position by engagement with said piston at its related end position of travel and also positioned to be exposed to pressure in its related working chamber to be moved to its actuating position.
 12. The apparatus as recited in claim 11, wherein said other positioning means comprises spring means which resiliently urges said control valve means to its intermediate position.
 13. The apparatus as recited in claim 9, further comprising other valve operating means having a first position wherein said first control chamber is exposed to low pressure, and a second position wherein said second control chamber is exposed to low pressure, whereby said control valve means can be moved between its first and second positions by operation of said other shifting valve means. Ap the effective pressure area of the high pressure piston
 14. A hydraulic power apparatus for operation as a pressure intensifying system to deliver a high pressure flow of output fluid, said apparatus comprising: a. a working cylinder, b. a working piston mounted in said working cylinder and separating said working cylinder into first and second working chambers, said working piston and cylinder being so arranged with inlet and outlet passage means as to receive pressurized working fluid of at least a predetermined pressure level alternately into said first and second working chambers, to cause said piston to reciprocate between opposite first and second end positions in said cylinder, c. first and second high pressure output piston means operatively connected to said working piston so as to be moved along reciprocating paths thereby to deliver a high pressure flow of output fluid, d. a control valve means to direct pressurized working fluid from a working fluid source alternately to said first and second working chambers to cause the reciprocation of said working piston,
 15. The apparatus as recited in claim 14, wherein said other valve positioning means for said control valve means comprises means to urge said control valve means to its intermediate position.
 16. The apparatus as recited in claim 14, wherein each of said shifting valve means comprises an actuating member extending into a related working chamber, whereby each of said actuating members is responsive to pressure in its related chamber as well as to engagement of said working piston. 